How to Treat Severe Laminitis in an Ambulatory Setting
Reprinted with permission from the American Association of Equine Practitioners.
|Fig. 1. (A) Biomechanical forces (GRF, moments about the DIP joint, and force of the DDFT) exert on the equine foot at rest. (B) The GRT moves into the toe and the moment around the DIP joint at the beginning of breakover.|
3. The Mechanism
The anatomic structure of the tissues affected bylaminitis has been well-documented. However, despiteconsiderable advances in our understating ofthe pathophysiology of laminitis made over the twodecades, there is still much to be learned about theinitiating events and the pathways by which theylead to the clinical disease. The interdigitatingdermal and epidermal lamellae and their relatedvasculature are positioned between the parietal surfaceof the distal phalanx and the rigid hoof capsule.The digital circulation to the proximal dorsal lamellaeis through the coronary artery, and the distaldorsal lamellae receive their blood supply frombranches of the terminal arch that form the circumflexartery. Any compromise or instability in thelamellae changes the position of the distal phalanx,which in turn, creates abnormal pressure on thevessels restricting circulation. The inflexible nature of the hoof capsule does not accommodate theinflammatory effects, especially edema, that occur inthe laminar tissue during laminitis—this scenariocould be considered a type of compartment syndromeeffect.
Knowledge of the biomechanics and forces exertedon the structures of the foot, including the lamellae,is critical to the clinicians when formulating a planto counteract these forces. Because the lamellaesuspend the distal phalanx within the hoof capsuleand accept weight, this structure is subjected to anarray of mechanical forces. The main forces are theweight (load) of the animal, which is opposed by theground reaction force (GRF) and the moments (amoment is the product of the length of a lever armand the force perpendicular to the lever arm) aboutthe distal interphalangeal (DIP) joint, in which themoment generated by the GRF is opposed by thatload generated by tension in the deep digital flexortendon (DDFT) (Fig. 1).4 These normal mechanicalforces exerted on the foot become detrimental withlaminar compromise. A laminitic horse that ispainful will be reluctant to move, and when notrecumbent, the horse's limbs will be approximatelypositioned as if in the mid-stance phase of the stride.The load (opposed by GRF) is located dorsal to thecenter of articulation and just behind and slightlymedial to the apex of the frog on the ground surfaceof the foot.5 When the limb is loaded, the tensileforces in the DDFT create a moment, which unlessopposed by an equal and opposite moment, causesrotation around the DIP joint. At breakover, themoment created by the DDF exceeds that created bythe GRF. The tensions in the DDF are greaterduring the mid-stance phase of the stride than atrest, and they are further increased at the beginningof the breakover phase of the stride. The opposingmoments generated by the GRF and the tension inthe DDF lead to a distractive force within the dorsallamellae. Dorsal capsular rotation is the most commonform of displacement seen in laminitis, and itrelates to the inability of the compromised lamellaeto accept the load placed on the dorsal region ofthe foot during weight-bearing and breakover.Through the action of these moments and weightbearing,the lamellae in the dorsal area of the foot are under more tensile strain compared with thelamellae in the quarters and heels, which along withthe frangible circulatory pattern in the dorsal sectionof the foot compared with the dual blood supplyin the palmar/plantar area of the foot, predisposethe dorsal lamellae to injury. The GRF determinesthe load and subsequent compressive and tensilestresses that are placed on the dorsal lamellae.The load or GRF on the foot cannot be changed, butthe position of the GRF (center of pressure) on theground surface of the foot can be shifted away fromthe affected area or redistributed. Support is aterm that is widely used, seldom defined, and oftenambiguous. Support usually means to hold a structurein place or prevent it from collapsing. In laminitis,it refers to supporting the distal phalanx andpreventing it from displacing from its normal positionwithin the hoof capsule. Attempting to counteractthe weight of the horse by any physical meansplaced under the foot makes this concept of supportunrealistic. The stresses on the lamellae are greatestduring weight-bearing and locomotion, and anattempt can be made to redirect these forces byrecruiting additional parts of the ground surface ofthe foot to bear weight to reduce the load on thelamellae. Decreasing the moment about the DIPjoint reduces the stresses on the lamellae that aregreatest during dorsiflexion of this joint. In a horsewith acute laminitis, the already damaged lamellaehave a greater propensity to separate with the stressassociated during breakover. Shortening the toedecreases the length of the lever arm, and elevatingthe heels decreases the tension in the DDFT.
Finally, the sole needs to be considered. In barefoothorses with a good foot, the conformation andthickness of the sole is not only protective but functional,and it can be considered a weight-bearingstructure. The sole in a shod horse has reducedfunctionality when it becomes suspended above theground surface of the foot with shoes, plays a limitedrole in weight-bearing, lacks stimulation, loses soledepth, and is often subjected to inappropriate farriery.In the routine practice of farriery, one of themost common causes of lameness is excessive solepressure in the presence of inadequate thickness ordepth. There are a plethora of pads, devices, andmaterials on the market that are placed on the soleor under the horse's foot to counteract the weight inthe early stage of laminitis. The rationale of thismethodology of creating excess pressure on theground surface of the foot in the face of insufficientsole depth has to be questioned. There are obviouslimitations of applying physical devices to the foot:we are limited to a relatively small surface area inan attempt to offset profound vertical forces imposedon the digit, the sole has a specific thickness, and theapplication of pressure through compromised tissuemay cause additional pain and tissue damage.5
4. Assembling the Team
The equine practitioner is responsible for addressingthe overall health and welfare of the horse. Whenconfronted with a serious case of laminitis, a farrierwill also play a prominent role in treatment and inmost cases of severe chronic laminitis, the predominantlong-term role. The team is completed withthe owner/trainer of the animal, who will often bethe primary caregiver, the party who makes thedecisions, and the person responsible for the financialobligations associated with the treatment.If either clinician (veterinarian or farrier) is inexperiencedin treating laminitis, it is prudent to seekadvice from or refer the case to an individual who isexperienced and treats this disease on a regularbasis. Current history, clinical impressions, andimages can be transmitted from the farm to a referralcenter for a consultation. There are a multitudeof methods/products available that all purport toimprove the disease, but none are proven or evenconsistent. There are no controlled studies documentingthe efficacy of any one medical or farrieryprocedure. Techniques change rapidly and for themost part, are empirical. Thus, laminitis treatmentremains anecdotal and is based on the stage ofthe disease, clinical experience of the clinician, andresponse of the patient. Because there is no proventreatment that is superior to the other, dialogue isimportant between both clinicians, because therewill be diverging thoughts, opinions, theories, andprevious treatment experiences. The preferred approachmay be to consider the individual case coupledwith the radiographs and decide on a treatmentstrategy based on medical and biomechanical principles.When communicating with the owner, thetreatment plan should always be presented in aconsensual manner. The clinicians should presenta unified approach to treatment, with neither partyquestioning the procedures of the other in front ofthe owner/trainer. Client communication is one ofthe most important but least discussed aspects ofcase management. A policy of open, honest communicationthat tempers false expectations of successmust be used. Owners should be givenrealistic information from the onset: severe laminitishas a poor prognosis, there are no proven treatments,any treatment can be extensive, expensive,and prolonged, and treatment may result in euthanasia.1,5,6 Given the seriousness of severe laminitis,clients will likely look into other sources forinformation or hope such as the internet, horse magazines,and support groups regarding the managementof their horse. It is imperative that theattending veterinarian and farrier are well-versedin the common inquiries that will arise and are ableto address them prospectively. Accurately predictingthe outcome of horses with laminitis is impossible.This lack of predictive power is understandablegiven the number of variables associatedwith management of severe laminitis, which includes not only the feet but the overall health of thepatient in addition to client constraints. The ownermust be warned that, if the horse with laminitis isinsured, it is their responsibility to inform the insurancecompany immediately.
|Table 1. The Lameness Scale Developed by Obel Can Be Used to Document Laminitis Severity|
Accurate assessment of the whole patient, with considerationfor history, occupation, and owner expectations,should be considered in every case whenattempting to provide appropriate treatment as wellas prognosis. Diagnostics remain basic for laminitis,but thoroughness must be emphasized. A completephysical examination and in particular,detailed evaluations of the feet are mandatory.Assessment of the intensity of the digital pulse, temperatureof the feet, and extent of lameness shouldbe made. The coronary band should be assessed forthe presence of edema, depressed areas that indicatedistal displacement, and palpably tender areas thatare associated with a possible abscess or separationof hoof wall. The shape and position of the sole isobserved for degree of concavity or protrusion, softspots, or excessive loss of depth. The size and conformationof the feet are especially important whendesigning a farriery plan for the horse and monitoringsubtle changes associated with the progressionof the disease. Hoof conformation may influenceloading patterns and the type of displacement encountered.For example, in the author's experience,there will generally be more displacement inan upright or club foot because of the increased loadon the dorsal lamellae caused by the pre-existingincreased tension in the DDFT and correspondingdorsal center of pressure. Conversely, horses witha long-toe/low-heel conformation generally havethin soles, which limits the use of the sole in counteractingthe weight of the horse.
In most instances, observation of the stance andgait provides a strong indication of the presence oflaminitis. The characteristic stilted camped-outfront legs are believed to redistribute load to thehindlimbs.5 Variations in stance likely occur becauseof the presence of pain in the rear feet orvariations in the location of pain in the front feet.It is not necessary to use local anesthesia to diagnoselaminitis, and it should be avoided if possible.The Obel grading system for lameness in laminitiscan be used to document the grade of laminitis andtrack the progression (Table 1).7
The clinician must determine the reason for andsource of pain, its location, and the degree of instability(amount of pain) within the foot. The locationof pain is important to determine from a therapeuticstandpoint, because any pressure applied under thisarea in an attempt to support the hoof will exacerbatethe pain. Hoof-tester evaluation is usefulwhen positive, but a negative response does not ruleout foot pain or laminitis. It is common to have anegative hoof-tester response in a horse with a thicksole and hoof capsule. Horses with metabolic syndrome also generally have a negative response.Hoof testers are also useful to assess the deformabilityof the sole, which gives a reasonable estimate ofsole depth. Bilateral diffuse solar pain across thetoe and dorsal wall is considered characteristic forlaminitis; however, bilateral foot bruising may yieldsimilar symptoms. Focal pain anywhere in the footis generally associated with sepsis or abscess formation,but the horse may assume a laminitic gait tounload on the foot. Hoof wall collapse along themedial quarter and heel is another recognized entityassociated with unilateral distal displacement of thedistal phalanx. A marked hoof-tester response isoften present in this area. It is not fully understoodwhether this is attributable to a greater degree oflamellar damage in this region or simply to regionalmechanical overload on that section of the foot.Variations of the stance and gait are recognizedwhen pain originates in areas other than the toe anddorsal wall. Laminitis involving the dorsal hoofwill generally present with a heel-first landing,whereas a horse with palmar foot pain will presentwith a toe-first gait or flat-footed landing. It is notuncommon for laminitic horses to land toe first, possiblybecause the stride is so shortened that theycannot extend the digit or because it is a deliberateaction to spread out the duration of loading the foot.
The most important determinant of prognosis inthe acute laminitic patient, and one of the mostdifficult to access, is the degree of instability betweenthe distal phalanx and hoof wall. At present,we have few, if any, means to make this assessmentbeyond the amount of pain, serial radiographs, thoroughclinical evaluation, and response to therapy.In the first 48 h of laminitis, pain has been shown tocorrelate well with the degree of histological injuryto the lamellae, making it a good predictor ofinstability.8
6. Acute Laminitis
When presented with a case of acute laminitis, threeproblems are encountered. First, there is no practicalmeans to assess the extent of the laminar damage present and if this damage will be permanentwhen the animal first shows clinical signs of acutelaminitis. The number of horses that suffer a severelaminitic episode that can be treated successfullyafter clinical signs are observed is alsorelatively small.3 The damage to the lamellae thatoccurs during the developmental stage of laminitisprecedes the onset of pain and lameness noted in theacute stage. Second, there is no practical means tocounteract the vertical load that is placed on thehorse's feet. Stated differently, we have no practicaldevice, product, or method that allows us to takethe weight off the compromised lamellae. Third,the distractive force placed on the lamellae by theDDFT is also hard to counteract.
Laminitis often originates from an organ systemremote from the foot, such as the gastrointestinal,respiratory, reproductive, or endocrine systems.Therefore, treatment during the acute stage needsto aggressively address the initiating cause of laminitis,or if treatment of the cause was initiated beforethe onset of clinical laminitis, it should becontinued. Recently, unequivocal evidence confirmsthat an inflammatory response is present veryearly in the disease before other changes are present,suggesting that the vascular changes, thrombiformation, and metalloproteinase degradation of thebasement membrane are downstream events.4The main pharmacologic agents used to treat theinflammatory response in early laminitis are nonsteroidalanti-inflammatory drugs (NSAIDs). Theanalgesic effects of NSAIDs are important from ahumane perspective but should be used judiciouslyso that the clinician is able to accurately monitor theclinical signs in the feet. Clinical improvementfrom the owners' perception is a decrease in pain;therefore, the clinician may be inclined to increasethe dose of NSAIDs or combine NASIDs to appeasethe client. This practice should be avoided, becausethe analgesic effects of the NSAIDs will increaseambulation and place additional stresses on thecompromised lamellae. The pharmacologic agentsmost frequently used to treat uncomplicated laminitisare phenylbutazone,b flunixin meglumine,c dimethylsulfoxide (DMSO),d and acepromazine.e4Unfortunately, there are no pharmacological agentsthat are of proven benefit after the initiating eventshave occurred. The purported anti-inflammatory,diuretic, and oxygen radial scavenging properties ofDMSO make it a logical choice. Experimentally,acepromazine increases digital and laminar bloodflow in normal horses, but it has not been tested inhorses with induced laminitis.9 Horses that havedeveloped laminitis associated with insulin resistance,such as in equine metabolic disease, may benefitfrom early intervention to increase insulinsensitivity.7 Measures should be taken immediatelyto reduce the weight of obese horses. The useof ice therapy in the acute stage of laminitis has been described, but its use outside of the developmentalstage remains somewhat controversial.7
Baseline radiographs consisting of a lateral and dorsopalmar(DP) 0° view should always be taken duringthe initial examination of acute laminitis ifpossible.3 The radiographs can be used to determineprevious damage, assess foot conformation,and guide initial hoof care. Serial radiographstaken at 2- to 4-day intervals during the instableperiod are used to follow the progression of displacementand speed of progression of the distal phalanx.Venography can be used to assess the circulatorypattern of the foot, but the clinician must be experiencedin performing the procedure and interpretingthe results.
|Fig. 2. Creased nail puller with short handles.|
|Fig. 3. Schematic representation of a laminitic horse standing in sand. Note that the properties of sand contour to the solar surface of the foot and allow the horse's toe to sink in the sand and elevate the heel. (Courtesy of Andrew Parks.)|
|Fig. 4. Wooden shoe attached to the foot with screws placed around the perimeter of the hoof wall and secured with casting tape.|
Physical measures are often applied to the foot bythe attending or consulting veterinarian during theacute stage of laminitis. The greatest overallstresses placed on the foot are associated withweight-bearing. To limit the focally increasedstresses placed on the foot during ambulation, it isimperative that an acute laminitic horse be restrictedto the stall. When a horse is shod or standingon a hard surface, the load is concentratedaround the perimeter of the hoof wall and transferredonto the lamellae. In acute laminitis, it isappropriate to remove the shoes, which is readilyaccomplished by removing individual nails with ashort-handled crease nail pullerf (Fig. 2). If thehorse is in extreme pain and reluctant to lift a foot,local anesthesia should be avoided, and sedation,such as detomidine hydrochloride,g should be usedto allow for removal of the shoes. Weight can beredistributed to the palmar/plantar section of thefoot by applying some type of deformable material tothe solar surface of the foot such that the sole, bars,and frog in the palmar section of the foot becomeload-sharing with the hoof wall. This redistributioncan be accomplished by applying thick Styrofoam,deformable impression material, or various pads and boots that are marketed for this purpose orplacing the horse in sand (Fig. 3). The author prefersto use beach sand if available. Caution mustbe used when employing the dorsal area of the soledistal to the dorsal margin of the distal phalanx andthe adjacent wall to bear weight. It should be notedthat recent biomechanical research has shown that,when the foot is loaded, the hoof expands or flaresout, and as a result, it pulls the sole distally.10Therefore, applying pressure to the sole in a horsewith minimal sole depth or one that shows painwhen hoof testers are applied may, in fact, compromisecirculation and increase the pain level. Applyingshoes in the acute stage of laminitis has notbeen shown to offer any advantages. In the acutestage of laminitis, the moments about the DIP jointand the distractive force placed on the lamellae bythe DDFT can be reduced to some extent by movingthe breakover in a palmar/plantar direction. A lineis drawn across the solar surface of the foot dorsal tothe frog, and a rasp is used to bevel the toe in adorsal direction from this line until it is approximately25-30° to the ground. This bevel effectivelymoves the breakover palmarly, decreases the pressureon the dorsal lamellae, and may lessen theforces created by the DDFT. Additionally, bevelingthe toe in this manner reduces weight-bearing bythe dorsal wall at rest. The center of pressure iseffectively moved in a palmar direction by extendingthe ground surface of the foot palmarly and applyingmild heel elevation. Raising the heels excessivelyin the acute stage has been advocated but should bedone with caution, because there is no scientificproof of a beneficial effect.
Laminitis as a consequence of various systemicdiseases and/or the administration of corticosteroidsoften results in distal displacement (sinking) of thedistal phalanx. In this case, the entire circumferentiallamina interface is damaged, allowing thedistal phalanx to descend or sink uniformly withinthe hoof capsule. There is minimal involvement ofthe DDFT during this process. The author has notfound elevating the heels in horses with distal displacementto be effective. Moving the breakoverback and placing a uniform layer of a deformableimpression material on the bottom of the foot orplacing the horse in sand may be a better option.4
Recently, the author favored the use of a woodenblock or shoe in horses with acute laminitis that areexpected to rotate or sink, and the results have beenvery encouraging. The flat solid construction allowsthe entire ground surface of the foot to be usedfor weight-bearing without excessive pressure onthe sole. The border of the ground surface of thewooden shoe can be beveled or cut on an angle,which seems to concentrate the load under the digit.The wooden shoe can be applied in a non-traumaticmanner, and the angle around the periphery of theshoe seems to decrease torque on the lamellae in thetoe and quarters. Two-inch fiberglass casting tapeis used to secure the block and limit expansion of thefoot (Fig. 4).
An acute case of laminitis should be reevaluatedat 48-72 h for improvement or worsening of thecondition. If the horse has not shown marked progress,the horse should be reassessed by the responsibleparties regarding treatment plans andalternatives. The prognosis becomes less optimistic.The client should also be aware that referralfacilities exist that provide additional options.
7. Chronic Laminitis
Rehabilitation of the horse with chronic laminitis isnot a cookbook process, because affected horses withchronic laminitis will vary from case to case and ourunderstanding of the disease is still vague. However,the understanding of digital mechanics hasimproved, and technological advances in shoe design/materials and techniques continue to expand.Chronic laminitis by definition means that the distalphalanx has displaced within the hoof capsule.11The distal phalanx can rotate down at the toe, rotateto either side (laterally or medially), or totally displace(sink) within the hoof capsule (Fig. 5). Rehabilitationof the horse with chronic laminitis willdepend on the amount of viable lamellae that remainintact, the conformation of the foot, and theability to realign the distal phalanx within the hoofcapsule. The question is often asked as to when toshoe a horse with chronic laminitis. The guidelinesthat may be used are when the horse is comfortable(stability), the horse is on minimal medication, andthe foot has been stabilized (i.e., there have been noadditional radiographic changes in the foot for agiven period of time). The author has not beensuccessful or observed improvement in the laminiticstate of any horse when having to use local anesthesiato lift the horse's foot and apply a shoe before thefoot has stabilized.
|Fig. 5. (A) Dorsal capsular rotation, (B) mediolateral rotation, and (C) distal displacement are illustrated.|
|Fig. 6. Radiograph of asymmetrical displacement of the distal phalanx on the medial side. Note that the solar foramens are not parallel with the ground. Also note the disparity in the joint space from the lateral to the medial side.|
|Fig. 7. A schematic representation of a lateral radiograph of a foot with dorsal capsular rotation can be used as a template when trimming. A line is drawn approximately parallel and about 15 mm distal to the solar surface of the distal phalanx. A second line is drawn parallel and approximately 15-18 mm dorsal to the parietal surface of the distal phalanx. The arrow at the intersection of the two lines is the farthest dorsal point that the toe of the shoe should be set. The second arrow is approximately 6 mm dorsal to the dorsal margin of the distal phalanx, and it is the approximate location of the point of breakover. (Courtesy of Andrew Parks.)|
The lateral radiograph is often the only film takenfor evaluating chronic laminitis, but it does not allowidentification of asymmetrical medial or lateraldistal displacement. Therefore, the author considersit crucial that a DP radiographic projection isincluded as part of the radiographic study for eitheracute or chronic laminitis.12 High-quality radiographsare required to visualize the osseous structureswithin the hoof capsule as well as the hoofcapsule itself. The radiographic features of chroniclaminitis are well-documented.13 The following observationsfrom the lateral radiograph are importantin determining the prognosis and guidingtreatment: the thickness of the dorsal hoof wall,the degree of dorsal capsular rotation, the angle ofthe solar surface of the distal phalanx relative to theground, the distance between the dorsal margin ofthe distal phalanx and the ground, and the thicknessof the sole.
The DP radiograph is examined to determine theposition of the distal phalanx in the frontal plane.Asymmetrical distal displacement of the distal phalanxon either the lateral or medial side is present ifa line drawn across the articular surface of the DIPjoint or between the solar foramens of the distalphalanx is not parallel to the ground, the joint spaceis widened on the affected side and narrowed on the opposite side, and the width of the hoof wall appearsthicker than normal on the affected side (Fig. 6).
Finally, radiology will form the guidelines to beused in realigning the distal phalanx and applyingany type of farriery (Fig. 7).
Farriery for Chronic Laminitis
Trimming and shoeing has always been the mainstayof treating chronic laminitis, and it is directedat reducing/removing the adverse forces on the compromisedlamellae. In considering hoof care inhorses with chronic laminitis, there are three goalsfor therapy: to stabilize the distal phalanx withinthe hoof capsule, control pain, and encourage newhoof growth to assume the most normal relationshipto the distal phalanx possible.12 Realignment ofthe distal phalanx to create a better relationship ofthe solar surface of the distal phalanx with theground is used as the basis for treating chronic laminitis.14,15 Realignment of the distal phalanxshould promote and produce hoof wall growth at thecoronet and sole growth distal to the distal phalanx.Using the radiographs as a template, the objective ofthe trim is to reposition the distal phalanx within the hoof capsule and realign the ground surface ofthe hoof capsule with the solar margin of the distalphalanx (Fig. 8). Applying any type of shoe afterthis procedure should complement the realignmentof the distal phalanx and decrease the forces on thelamellae. The shoeing principles applied to allshoeing methods used in treating chronic laminitisare to recruit ground surface, reposition the breakoverpalmarly, and provide heel elevation asneeded.12,14 The author's shoe of choice is usually awide-web aluminum shoe with heel elevation eitherincorporated into the shoe in the form of rails or byusing a bar wedge inserted between the shoe and thesolar surface of the foot. Deformable impressionmaterialh can be applied between the branches ofthe shoe to increase the surface area and redistributethe load. Breakover can easily be placed intothe shoe in the appropriate place by forging or usingan electrical grinder. The middle of the foot is usedfor accurate placement of the shoe on the foot.12
Recently, the author has been very successful attreating selected cases of chronic laminitis using awooden block cut in the shape of the foot with theborder of the ground surface cut on an angle of atleast 45° (Fig. 9).12,14,16,17 The foot is trimmed appropriatelyto address realignment; impression materialis used judiciously in the palmar section of thefoot to create a solid plane between the solar surfaceof the foot and the wooden shoe. Heel elevation canbe incorporated into the wooden shoe if necessary,and the shoe is applied atraumatically using screwsand casting tape. With this method, there is flat,even pressure placed across the palmar section ofthe foot, and all the mechanics are placed in theblock while preserving the hoof capsule.
|Fig. 8. A schematic diagram of a horse's foot with rotation before (A) and after being trimmed (B) according to guidelines in Fig. 7. Note that in C, the dorsal and palmar aspects of the ground surface now form two different planes. (Courtesy of Andrew Parks.)|
|Figure 9. A wooden shoe applied to the foot. Note the screws are inserted against the hoof wall and the point of breakover on the ground surface of the shoe corresponds with a vertical line drawn from the coronet.|
|Fig. 10. Lateral and DP radiograph of a horse with severe laminitis. The displacement of the distal phalanx, the position of the coronet, the disruption of the lamellae, and the solar penetration will prevent recovery.|
DDF tenotomy remains a very useful procedure fortreating chronic laminitis. The author considersthis surgery necessary if the margin of the distalphalanx has prolapsed through the sole or in thosecases that fail to stabilize after they begin displacing.As stated earlier, two of the main detrimentswhen treating chronic laminitis are the weight of thehorse and the distractive force of the DDFT. One ofthese detrimental forces can be removed throughthis surgery, but knowing when to use it poses adilemma. It is often necessary to use this procedureto realign the distal phalanx. Additional indicationsfor this surgery are progressive rotation, persistent pain, minimal hoof wall and/or solegrowth, and secondary flexor apparatus contracture.If there is a marked flexural deformity involving theDIP joint present, it indicates shortening of the musculotendonousunit, and a release procedure is necessaryto accomplish realignment of the distalphalanx. It has to be emphasized that, if a DDFtenotomy is used, it must be accompanied by realignmentof the distal phalanx to decrease the adverseforces on the lamellae. After a DDFtenotomy, the middle phalanx will move distally andpalmarly relative to the distal phalanx. This movementconcentrates the load on the palmar soft-tissuestructures of the foot rather than redistributing theload on the solar surface of the distal phalanx.The author has found it helpful to use a shoe orwedge pad attached to a cuff to extend the groundsurface beyond the heel of the hoof capsule and adda few degrees of heel elevation. This elevation willrealign the digital axis, and it seems to improve theclinical parameters (comfort, hoof capsule changes,sole growth, etc.) after surgery.12
The clinicians should continually discuss the humaneissues surrounding a case of severe laminitisfrom the onset. This discussion is especially importantin laminitis cases that have the potential or aredisplaying clinical and radiographic signs of distaldisplacement (sinking), because these cases inevitablyhave a poor prognosis. From a humane aspect,it is irresponsible to prolong the life of a chronicallypainful horse with no chance of recovery or anyquality of life. The decision for euthanasia is oftensubjective, and the clinician must take into considerationthe owner's psychological attachment to thehorse. Monetary and insurance considerationsmust be discussed frankly. Convincing evidencecan and should be presented to the owner, such asduration of the current treatment, status of thehorse (unrelenting pain, recumbency, or weightloss), foot conformation (no hoof or sole growth, prolapseof distal phalanx through the sole, or palpabletrough at the coronet), and imaging (severe displacement-rotation and/or sinking, position of coronet,or irreversible damage to the hoof capsule) (Fig. 10).If a decision is reached to euthanize a horse, thedecision should be unanimous among all the membersof the team. The clinician should recommendand encourage the owner to seek a second opinion.The attending or consulting veterinarian or farriershould never imply to the owner that a differentapproach or mode of therapy initiated at a particulartime would have changed the outcome of the case.There is no scientific evidence to support such aderogatory statement, it casts doubt on the professionalismof the clinicians involved, and it opens thedoor for possible litigation.
Unfortunately, many of the treatment regimens,both medical and farriery techniques, used to treatacute and chronic laminitis are based on tradition,theoretical assumptions that a given treatmentshould work, and anecdotal evidence that a certaintype of treatment has worked on previous cases.There are no controlled studies confirming or comparingthe efficacy of the numerous treatments inuse, and there is no scientific proof that one treatmentis superior to another treatment. What iswell-documented are the forces and mechanics applicableto the equine foot. Clinicians (veterinariansand farriers) may be better served by a thoroughknowledge and understanding of the anatomy, physiology,and function of the hoof. Understanding thefoot in a mechanical sense may allow for betterapplication of a preferential treatment protocol.
Treatment of laminitis has to be a team effortequally shared between veterinarian, farrier, andowner. The intent of this paper is not to discouragetreatment of laminitis but to create expectationsthat are realistic, humane, and based on thecause of the disease, amount of lamellar damage,pain, duration, and financial constraints involvedin prolonged treatment. At the onset of treatingsevere laminitis, certain guidelines can andshould be outlined to indicate the efficacy of thechosen treatment method along with a reasonable time frame for improvement. These guidelinescould be a change in stance, decreased digitalpulse, increased comfort, horn growth at the coronet,sole growth, etc. If the desired improvementis not observed or the condition gets worse,the overall farriery methods should be reassessedand changed where necessary.
With severe laminitis cases, we are often unableto rehabilitate the horse to where it has an acceptablequality of life. The main reason is that thereare insufficient laminar structures remainingwithin the hoof to achieve realignment and acceptweight. The author feels that it is important, froma humane perspective, to know when to discontinuetreatment that has not been effective. Often, wepersevere with various treatments, putting thehorse through much unnecessary suffering, only toachieve an unsatisfactory outcome. It is unlikelythat this disease can ever be fully eliminated, and itis unlikely that there will ever be a single drug orother line of therapy to consistently treat acute orchronic laminitis; therefore, our clinical and researchefforts should be divided between preventionand treatment.
References and Footnotes